From: Edwin Fine <efine145-nospam01@...>
Date: 2006-12-09T16:20:18+09:00
Subject: Re: Am I missing something about BER-compressed integer?

Francis Cianfrocca wrote:
> On 12/8/06, Francis Cianfrocca <garbagecat10@gmail.com> wrote:
>> but I expected to get:
>>
>>
> 
> 
> I figured it out. There's no bug in Ruby. pack("w") produces the
> integer representation that's occasionally used in BER to save space
> when representing things like OIDs, not the "standard" BER
> representation that requires a field-size prefix.

Ruby uses BER as specified by Perl. Excerpt from the perlpacktut page:

The pack code w has been added to support a portable binary data 
encoding scheme that goes way beyond simple integers. A BER (Binary 
Encoded Representation) compressed unsigned integer stores base 128 
digits, most significant digit first, with as few digits as possible. 
Bit eight (the high bit) is set on each byte except the last. There is 
no size limit to BER encoding, but Perl won't go to extremes.
---------
Applying the above rules:

irb(main):045:0> printf("%08b%08b", 0b10000000 | (9999/128), 9999%128)
1100111000001111=> nil

Ruby:

irb(main):046:0> [9999].pack("w").each_byte { |b| printf("%08b", b) }
1100111000001111=> "\316\017"


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